A new adaptive technique of r-and h-version for vibration problemsutilizing the matrix per- turbation theory and element energy ratiois proposed. In structural vibration analysis, through the r-conver-gence adaptvie f...A new adaptive technique of r-and h-version for vibration problemsutilizing the matrix per- turbation theory and element energy ratiois proposed. In structural vibration analysis, through the r-conver-gence adaptvie finite element process, mesh optimization can berealized. In the light of the judgement on the changes in themagnitude of the element energy ratio, local refinement can beachieved in the process of h- convergence adaptive finite element sothat more accurate finite element solutions can be obtained with asfew meshes as possible. Many numerical examples are given and theproposed approach is shown to be feasible and effective.展开更多
An h-adaptive method is developed for high-order discontinuous Galerkin methods(DGM)to solve the laminar compressible Navier-Stokes(N-S)equations on unstructured mesh.The vorticity is regarded as the indicator of adap...An h-adaptive method is developed for high-order discontinuous Galerkin methods(DGM)to solve the laminar compressible Navier-Stokes(N-S)equations on unstructured mesh.The vorticity is regarded as the indicator of adaptivity.The elements where the vorticity is larger than a pre-defined upper limit are refined,and those where the vorticity is smaller than a pre-defined lower limit are coarsened if they have been refined.A high-order geometric approximation of curved boundaries is adopted to ensure the accuracy.Numerical results indicate that highly accurate numerical results can be obtained with the adaptive method at relatively low expense.展开更多
The study on the fingering phenomenon has been playing an important role in understanding the mechanism of the fluid flow through the porous media.In this paper,a numerical method consisting of the Crank-Nicolson sche...The study on the fingering phenomenon has been playing an important role in understanding the mechanism of the fluid flow through the porous media.In this paper,a numerical method consisting of the Crank-Nicolson scheme for the temporal discretization and the finite element method for the spatial discretization is proposed for the relaxation non-equilibrium Richards equation in simulating the fingering phenomenon.Towards the efficiency and accuracy of the numerical simulations,a predictor-corrector process is used for resolving the nonlinearity of the equation,and an h-adaptive mesh method is introduced for accurately resolving the solution around the wetting front region,in which a heuristic a posteriori error indicator is designed for the purpose.In numerical simulations,a traveling wave solution of the governing equation is derived for checking the numerical convergence of the proposed method.The effectiveness of the h-adaptive method is also successfully demonstrated by numerical experiments.Finally the mechanism on generating fingers is discussed by numerically studying several examples.展开更多
For the numerical simulation of compressible flows,normally different mesh sizes are expected in different regions.For example,smaller mesh sizes are required to improve the local numerical resolution in the regions w...For the numerical simulation of compressible flows,normally different mesh sizes are expected in different regions.For example,smaller mesh sizes are required to improve the local numerical resolution in the regions where the physical variables vary violently(for example,near the shock waves or in the boundary layers)and larger elements are expected for the regions where the solution is smooth.h-adaptive mesh has been widely used for complex flows.However,there are two difficulties when employing h-adaptivity for high-order discontinuous Galerkin(DG)methods.First,locally curved elements are required to precisely match the solid boundary,which significantly increases the difficulty to conduct the"refining"and"coarsening"operations since the curved information has to be maintained.Second,h-adaptivity could break the partition balancing,which would significantly affect the efficiency of parallel computing.In this paper,a robust and automatic h-adaptive method is developed for high-order DG methods on locally curved tetrahedral mesh,for which the curved geometries are maintained during the h-adaptivity.Furthermore,the reallocating and rebalancing of the computational loads on parallel clusters are conducted to maintain the parallel efficiency.Numerical results indicate that the introduced h-adaptive method is able to generate more reasonable mesh according to the structure of flow-fields.展开更多
In this work,we extend the characteristic-featured shock wave indicator based on artificial neuron training to 3D high-speed flow simulation on unstructured meshes.The extension is achieved through dimension splitting...In this work,we extend the characteristic-featured shock wave indicator based on artificial neuron training to 3D high-speed flow simulation on unstructured meshes.The extension is achieved through dimension splitting.This leads to that the proposed indicator is capable of identifying regions of flow compression in any direction.With this capability,the indicator is further developed to combine with h-adaptivity of mesh refinement to improve resolution with less computational costs.The present indicator provides an attractive alternative for constructing high-resolution,high-efficiency shock-processing methods to simulate high-speed inviscid flows.展开更多
基金the National Natural Science Foundation of China (No.19872029)
文摘A new adaptive technique of r-and h-version for vibration problemsutilizing the matrix per- turbation theory and element energy ratiois proposed. In structural vibration analysis, through the r-conver-gence adaptvie finite element process, mesh optimization can berealized. In the light of the judgement on the changes in themagnitude of the element energy ratio, local refinement can beachieved in the process of h- convergence adaptive finite element sothat more accurate finite element solutions can be obtained with asfew meshes as possible. Many numerical examples are given and theproposed approach is shown to be feasible and effective.
基金supported by the National Natural Science Foundation of China(11272152)
文摘An h-adaptive method is developed for high-order discontinuous Galerkin methods(DGM)to solve the laminar compressible Navier-Stokes(N-S)equations on unstructured mesh.The vorticity is regarded as the indicator of adaptivity.The elements where the vorticity is larger than a pre-defined upper limit are refined,and those where the vorticity is smaller than a pre-defined lower limit are coarsened if they have been refined.A high-order geometric approximation of curved boundaries is adopted to ensure the accuracy.Numerical results indicate that highly accurate numerical results can be obtained with the adaptive method at relatively low expense.
基金supported by FDCT of Macao SAR(FDCT 029/2016/A1),MYRG of University of Macao(MYRG2017-00189-FST,MYRG2019-00154-FST)National Natural Science Foundation of China(Grant Nos.11922120,11871489,and 11401608)Department of Science and Technology of Guangdong Province.
文摘The study on the fingering phenomenon has been playing an important role in understanding the mechanism of the fluid flow through the porous media.In this paper,a numerical method consisting of the Crank-Nicolson scheme for the temporal discretization and the finite element method for the spatial discretization is proposed for the relaxation non-equilibrium Richards equation in simulating the fingering phenomenon.Towards the efficiency and accuracy of the numerical simulations,a predictor-corrector process is used for resolving the nonlinearity of the equation,and an h-adaptive mesh method is introduced for accurately resolving the solution around the wetting front region,in which a heuristic a posteriori error indicator is designed for the purpose.In numerical simulations,a traveling wave solution of the governing equation is derived for checking the numerical convergence of the proposed method.The effectiveness of the h-adaptive method is also successfully demonstrated by numerical experiments.Finally the mechanism on generating fingers is discussed by numerically studying several examples.
基金supported by the funding of the Key Laboratory of Aerodynamic Noise Control(No.ANCL20190103)the State Key Laboratory of Aerodynamics(No.SKLA20180102)+1 种基金the Aeronautical Science Foundation of China(Nos.2018ZA52002,2019ZA052011)the National Natural Science Foundation of China(Nos.61672281,61732006)。
文摘For the numerical simulation of compressible flows,normally different mesh sizes are expected in different regions.For example,smaller mesh sizes are required to improve the local numerical resolution in the regions where the physical variables vary violently(for example,near the shock waves or in the boundary layers)and larger elements are expected for the regions where the solution is smooth.h-adaptive mesh has been widely used for complex flows.However,there are two difficulties when employing h-adaptivity for high-order discontinuous Galerkin(DG)methods.First,locally curved elements are required to precisely match the solid boundary,which significantly increases the difficulty to conduct the"refining"and"coarsening"operations since the curved information has to be maintained.Second,h-adaptivity could break the partition balancing,which would significantly affect the efficiency of parallel computing.In this paper,a robust and automatic h-adaptive method is developed for high-order DG methods on locally curved tetrahedral mesh,for which the curved geometries are maintained during the h-adaptivity.Furthermore,the reallocating and rebalancing of the computational loads on parallel clusters are conducted to maintain the parallel efficiency.Numerical results indicate that the introduced h-adaptive method is able to generate more reasonable mesh according to the structure of flow-fields.
基金supported by the National Numerical Wind Tunnel Project,the National Natural Science Foundation of China(No.12001031)the Academic Excellence Foundation of BUAA for PhD Students,China Postdoctoral Science Foundation(No.2020M680284).
文摘In this work,we extend the characteristic-featured shock wave indicator based on artificial neuron training to 3D high-speed flow simulation on unstructured meshes.The extension is achieved through dimension splitting.This leads to that the proposed indicator is capable of identifying regions of flow compression in any direction.With this capability,the indicator is further developed to combine with h-adaptivity of mesh refinement to improve resolution with less computational costs.The present indicator provides an attractive alternative for constructing high-resolution,high-efficiency shock-processing methods to simulate high-speed inviscid flows.
